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Award Ceremony Speech

This year's Nobel prize in Physics is shared equally between
Sheldon Glashow, Abdus Salam and Steven Weinberg "for their
contributions to the theory of the unified weak and
electromagnetic interaction between elementary particles,
including inter alia the prediction of the weak neutral
current".

Important advances in physics often consist
in relating apparently unconnected phenomena to a common cause. A
classical example is Newton's introduction of the gravitational
force to explain the fall of the apple and the motion of the moon
around the earth. - In the 19th century it was found that
electricity and magnetism are really two aspects of one and the
same force, the electromagnetic interaction between charges.
Electromagnetism, with the electron playing the leading part and
the photon - the electromagnetic quantum of light - as the swift
messenger, dominates technology and our everyday life: not only
electrotechnics and electronics, but also atomic and molecular
physics and hence chemical and biological processes are governed
by this force.

When one began to study the atomic nucleus
in the first decades of our century, two new forces were
discovered: the strong and the weak nuclear forces. Unlike
gravitation and electromagnetism these forces act only over
distances of the order of nuclear diameters or less. The strong
force keeps the nucleus together, whereas the weak force is
responsible for the so called beta decays of the nucleus. Most
radioactive substances used in medicine and technology are beta
radioactive. The electron also participates in the weak
interaction, but the principal part is played by the neutrino, a
particle which is described as follows in a poem by the American
writer John Updike:

"Cosmic Gall"

Neutrinos, they are very small.
They have no charge and have no mass
And do not interact at all.
The earth is just a silly ball
To them, through which they simply pass,
Like dustmaids down a drafty hall
Or photons through a sheet of glass.
- - -
At night, they enter at Nepal
And pierce the lover and his lass
From underneath the bed - you call
It wonderful; I call it crass.

The description is accurate, apart from the
statement 'they do not interact at all'; they do interact through
the weak force. The neutrinos of the poem, entering the earth at
night at Nepal and exiting in the U.S. in a sort of reversed
China syndrome, come to us from the centre of the sun. Solar
energy, necessary for life on earth, is created when hydrogen is
burnt to helium in the interior of the sun in a chain of nuclear
reactions - even the advocates of "Solsverige" must ultimately
rely on nuclear energy although it must be said that the fusion
reactor Sun is well encapsuled and sufficiently relocated away
from populated areas. The first ignating and moderating link in
this chain, burning hydrogen to deuterium, is based on the weak
force, which could then be called the Sunignator and
Suntamer.

The theory which is awarded this year's
prize, and which was developed in separate works by the
prizewinners in the 60's, has extended and deepened our
understanding of the weak force by displaying a close
relationship to the electromagnetic force: these two forces
emerge as different aspects of a unified electroweak interaction.
This means e.g. that the electron and the neutrino belong to the
same family of particles; the neutrino is the electron's little
brother. Another consequence of the unified theory is that there
should exist a new kind of weak interaction. It was formerly
assumed that weak processes could occur only in connection with a
change of identity of the electron to neutrino (or vice versa);
such a process is said to proceed by a charged current, since the
particle changes its charge. The theory implies that there should
also be processes connected with a neutral current in which the
neutrino - or else the electron - acts without changing identity.
Experiments in the 70's have fully confirmed these predictions of
the theory.

The importance of the new theory is first
of all intrascientific. The theory has set a pattern for the
description also of the strong nuclear force and for efforts to
integrate further the interactions between elementary
particles.

Let me end by giving an example of the
intricate links which exist between different branches of natural
science.

Our body is to a large part constructed
from "stardust": the elements besides hydrogen which build our
cells have been formed in the interior of stars in nuclear
reactions, which form a continuation of the processes taking
place in our sun. According to the astrophysicists, certain heavy
elements appearing in life-important enzymes and hormones -
iodine and selenium are examples of such elements - can probably
only be created in connection with violent explosions of giant
stars, so called supernova explosions, which occur in our Galaxy
once every one or two hundred years. It is likely that neutrinos
interacting via the neutral current play an important role in
these explosions, in which a large part of the matter of the star
is thrown out into space. Thus, for our functioning as biological
beings we rely on elements formed milliards of years ago in
supernova explosions, with the new kind of weak force predicted
by the theory contributing in an important way; really a
fascinating connection between biology, astrophysics and
elementary particle physics.

Professors Sheldon Glashow, Abdus Salam,
and Steven Weinberg,

In my talk I have tried to give a background to your great
discoveries in the borderland between a strange but known country
and the probably large unknown territory of the innermost
structure of matter.

Our way of looking at this structure has
changed radically in the last decade. The theory of electroweak
interaction has been one of the most important forces to bring
about this change of outlook.

It is a privilege and a pleasure for me to
convey to you the warmest felicitations of the Royal Swedish
Academy of Sciences and to invite you to receive your prizes from
the hands of his Majesty the King.